In the summer of 2007 Antonelli was loaned out to Serie B club Bari, but he impressed so much that during the January transfer window Parma secured him on loan from Milan for the rest of the Serie A season. He made his first appearance for the Gialloblu against Livorno on 16 March 2008.

In June 2008, Parma had acquired half of the contractual rights from Milan, for €750,000.[1] While the following summer, he was fully transferred for another €2.5 million, which Milan made a final income of €1.75 million as the value of the retained half had increased from €0.75 million to €2.5 million.[1][2]

In February 2015, Antonelli moved back to his debut club Milan, signing a three-and-a-half-year contract.[4] On his debut for his return to Milan on 7 February 2015, Antonelli scored a goal from a corner kick off a header to tie the match with Juventus at 1-1, which did not prove decisive, as Milan fell 3-1 final.